1. Field of the Invention
The present invention relates to a remote control transmitter to remotely control electric devices, and more particularly to a remote control transmitter suited to be used for an image projector.
2. Description of the Related Art
It is known to use a remote control transmitter to remotely control electric devices. A light emitting diode is used as a light source for remote control in the remote control transmitter. In some cases, the remote control transmitter is used to control an electric device such as image projector that is placed in a wide space and remotely controlled. The remote control transmitter for such use is required to have a long transmission distance and a wide transmittable angle (wide directivity). For this reason, as shown in FIG. 5A and FIG. 5B, a conventional remote control transmitter 101 has a pair of light emitting diodes 111a and 111b. The pair of light emitting diodes 111a and 111b have substantially the same electrical and optical characteristics, and are mounted in holders 112a and 112b and placed side by side at A front end 110 of the remote control transmitter 101. The remote control transmitter 101 transmits remote control signals to electric devices according to operation of an operating unit 120 by a user.
The light emitting diodes 111a and 111b have transmission ranges La and Lb. In order to extend the transmission distance of the remote control signals, the light emitting diodes 111a and 111b are so placed at the front end 110 that respective maximum radiation directions C′ each giving a maximum radiation intensity are parallel to each other. By providing the two light emitting diodes 111a and 111b in such manner, the remote control transmitter 101 is enhanced in its capability to transmit the remote control signals and improved in its operability.
However, according to such conventional remote control transmitter 101, it has not been possible to significantly widen its transmittable angle although its capability of long distance transmission can be significantly improved by using the two light emitting diodes 111a and 111b. 
Meanwhile, an attempt has been made for a known remote control transmitter to have both the capability of long distance transmission and wide directivity by using a light emitting diode with wide directivity in combination with a light emitting diode with narrow directivity (refer to e.g. Japanese Laid-open Patent Publication Hei 8-168083). The remote control transmitter disclosed therein is to be used for door locking apparatus for cars. According to such known remote control transmitter, it is possible to obtain wide directivity in short distance areas by using the combination of wide directivity and narrow directivity light emitting diodes. However, it is not possible to obtain wide directivity in long distance areas. In other words, such remote control transmitter may be suited to remotely control the door locking apparatus for cars, but cannot contribute to much improvement of operability of electric devices such as an image projector to be usually placed distantly from a user in a wide space.
Besides, there is known a light emitting device, in which a lens having a shape such as cylinder is provided on the front face of the light emitting element, in order to make it possible to widen the emission angle (refer to e.g. Japanese Laid-open Patent Publication 2000-353813). However, it cannot extend the transmission distance.